1. Field of the Invention
This invention relates to a stitchbonded nonwoven fabric and a process for making such fabric. More particularly, the invention concerns a stitchbonded fabric having a pattern of stitches formed by a stitching thread that comprises fibers consisting essentially of partially oriented synthetic organic polymer. The stitchbonded nonwoven fabric is particularly suited for use in thermoformed objects, such as automobile dashboards and headliners, office separator walls, wall coverings, plastic-coated or resin-impregnated fabrics and the like.
2. Description of the Prior Art
Stitchbonded nonwoven fabrics and processes and machines for making such fabric are known.
Stitchbonded nonwoven fabric is made by multi-needle stitching of a fibrous layer with one or more stitching thread systems to form patterns of stitches in the layer. Known processes for making a stitchbonded nonwoven fabric typically include the steps of (a) feeding a fibrous layer to a stitchbonding machine; (b) threading a multi-needle bar of the stitchbonding machine with stitching threads; (c) inserting the stitching thread into the fibrous layer to form a pattern of spaced apart, interconnected rows of stitches, thereby creating the stitchbonded fabric; (d) removing the stitchbonded fabric from the stitchbonding machine; and (e) optionally subjecting the stitchbonded fabric to further textile finishing operations, such as shrinking, heat setting, molding, coating, impregnating and the like.
Stitchbonded nonwoven fabrics that include stitching threads of conventional, fully drawn, crystalline polymeric yarns (also called xe2x80x9chard yarnsxe2x80x9d) are known. Although the use of stitching threads of such fully drawn yarns has been quite successful in many stitchbonded fabrics, such fabrics nonetheless have certain shortcomings. For example, such stitchbonded fabrics, although dimensionally stable, usually perform inadequately in molding or thermoforming operations.
Stitchbonded nonwoven fabrics that include stitching threads of spandex elastic yarns, which are capable of elongating and contracting in the range of 100 to 250%, also are known. (Spandex is a generic term for a manufactured fiber in which the fiber-forming substance is a long chain elastomer comprised of at least 85% segmented polyurethane.) The use of such elastic stitching thread, with or without an accompanying non-elastic thread, is disclosed in my earlier patents; for example, in U.S. Pat. Nos. 4,876,128, 4,773,238, 4,737,394 and 4,704,321 for making bulky and/or stretchy stitchbonded fabrics, in WO 94/19523 for making abrasion-resistant resin-impregnated stitchbonded fabrics, and in U.S. Pat. No. 5,308,674 for making tear-resistant stitchbonded fabric. According to the processes disclosed in each of these patents, the stitchbonded fabric, immediately upon removal from the multi-needle stitching operation, is allowed to shrink and gather and thereby undergo a significant reduction in fabric area. Although such spandex-containing stitchbonded nonwoven fabrics have been used successfully in a variety of products, further improvements, particularly in dimensional stability, would result in broader use of stitchbonded nonwoven fabrics. Accordingly, a stitchbonded fabric is desired that has lower costs and fewer special handling and stitching control requirements than those associated with stitchbonded fabric containing spandex elastic yarn.
The present invention provides an improved stitchbonded nonwoven fabric. The fabric is of the type that includes a fibrous layer and patterns of stitches inserted therein with stitching threads. According to the improvement of the invention, at least one stitching thread consists essentially of fiber of partially molecularly oriented synthetic organic polymer. In one preferred embodiment, all the stitching thread is yarn of fiber of such partially oriented polymer. In another embodiment of the invention, the stitchbonded fabric has additional patterns of stitches formed by stitching threads of textured yarn of drawn fiber of synthetic organic polymer.
The present invention also provides an improved process for making the above-described stitchbonded nonwoven fabric. The process is of the type that includes feeding a layer of substantially nonbonded fibers to a stitchbonding machine having at least one multi-needle stitching bar, threading a needle bar with stitching thread, inserting a pattern of stitches with the threaded multi-needle stitching bar into the layer of substantially nonbonded fibers to form the stitchbonded nonwoven fabric and then optionally subjecting the stitchbonded nonwoven fabric to stretching, shrinking, heat setting, coating, impregnating or other textile operations. The improvement of the process of the invention comprises the stitching thread in at least one multi-needle stitching bar consisting essentially of fiber of partially molecularly oriented synthetic organic polymer. A preferred stitching thread consists essentially of fibers of partially molecularly oriented polyester.